This invention relates to a special effect picture device for generating a non-linear transformed picture of an original picture using the information of the original picture.
It is practiced to perform special effect processing on picture signals using a buffer memory. For example, special effect processing is executed by controlling the write address for writing picture signals into a frame buffer memory or by controlling the read-out address for reading out the picture signals from the frame buffer memory.
Examples of the special effect processing include linear picture transformation, such as contraction, enlargement, movement or rotation, ripple effects which is producing moire pictures, or superimposition of a transformed picture on itself (on the original picture), and non-linear effects, such as page-turning effect comparable to folding of a book page. The special effect processing is performed by a special effect picture device.
The special effect processing, performed by the special effect picture device, is basically the synthesis of picture signals. For example, two signals, that is a video signal V.sub.1 shown in FIG. 1A and a key signal K shown in FIG. 1B, and another signal, which is a background signal V.sub.2, are synthesized by a switcher for outputting a synthesized signal O shown in FIG. 1C.
Specifically, the above special effect picture device outputs the synthesized signal O by the technique explained with reference to FIG. 2. The input video signal V.sub.1 shown in FIG. 1A and the key signal K shown in FIG. 1C are multiplied by each other by a multiplier 70 to give a product V.sub.1 K. On the other hand, the key signal K is subtracted by a subtractive node 71 from "1" to give difference (1-K) which is then multiplied by the background signal V.sub.2 by a multiplier 72 to give a product V.sub.2 (1-K). The product V.sub.2 (1-K) from the multiplier 72 is summed to the product V.sub.1 K from the multiplier 70 by an additive node 73 to give a synthesized output signal O such that EQU O=V.sub.1 K+V.sub.2 (1-K) (1)
In the equation (1), the boundary between the input video signal V.sub.1 and the background signal V.sub.2 is determined by the gradient of the key signal K.
The page turning effect, realized by the above special effect picture device, is explained with reference to FIG. 3.
The page turning effect is an effect of folding an input picture V at a position M. When observed from the lateral side, the folded portion is cylindrically-shaped. For folding, a coordinate system (X:Y:L) is necessary for representing the folding direction and a folding position M. An axis T represents the folding direction. In the coordinate system, X.sub.L on the x-axis and Y.sub.L on the y-axis represent linear addresses, that is, addresses used for linear transformation, such as contraction, enlargement, movement or rotation. The axis T is given by an equation EQU T=X.sub.L *cos .THETA.+Y.sub.L *sin .THETA. (2)
where .THETA. denotes an angle indicating the folding direction.
In FIG. 3, a lower picture V.sub.b, shown by a solid line, is situated ahead of an imaginary cylinder as far as the visual sense of the viewer is concerned. This may be conceived as being caused by transformation which shifts the linear addressees of the lower picture for compression along the T axis. A movement function f.sub.D (T) representing the movement of the lower picture is given by EQU f.sub.D (T)=-T+p-r*arcsin ((-T+p)/r) (3)
where r and p denote the radius and the center of the imaginary cylinder, respectively.
The components of the linear addresses (X.sub.L, Y.sub.L) shown by the equation (2) are each added to with the movement function multiplied by cos .THETA. and sin .THETA.. Thus the X-axis read-out address X.sub.DL and the Y-axis read-out address Y.sub.DL of the lower picture of the page-turning effect are given by EQU X.sub.DL =X.sub.L +f.sub.D (T)*cos .THETA. (4) EQU Y.sub.DL =Y.sub.L +f.sub.D (T)*sin .THETA. (5)
On the other hand, if the movement function indicating the movement of an upper picture is represented by f.sub.U (T), the X-axis read-out address X.sub.UL and the Y-axis read-out address Y.sub.UL of the upper picture of the page-turning effect are given by EQU X.sub.UL =X.sub.L +f.sub.U (T)*cos .THETA. (6) EQU Y.sub.UL =Y.sub.L +f.sub.U (T)*sin .THETA. (7)
FIGS. 4B and 4C show characteristics of the movement function f.sub.D (T) representing the movement of the lower picture and the movement function f.sub.U (T) representing the movement of the upper picture, respectively. The movement function for the lower picture f.sub.D (T) and the movement function for the upper picture f.sub.U (T) are previously written in a static RAM used as a lookup table, under control by a central processing unit (CPU), and reference thereto may be had from the lookup table with the value of T as an address. FIG. 4A shows a curve for the folding portion of FIG. 3 as viewed from the lateral side.
FIG. 5 is an illustrative circuit diagram showing a page-turning address generating circuit for producing the read-out address for the lower picture and that for the upper picture shown by the equations (4) to (7).
Referring to FIG. 5, a linear address X.sub.L and cos .THETA. are routed to a multiplier 80, while a linear address Y.sub.L and sin .THETA. are routed to a multiplier 82. An additive node 81 adds the output X.sub.L *cos .THETA. of the multiplier 80 to the output Y.sub.L *sin .THETA. of the multiplier 82 to output an addition output X.sub.L *cos .THETA.+Y.sub.L *sin .THETA.. The addition output X.sub.L *cos .THETA.+Y.sub.L *sin .THETA. is T shown in the equation (2). Any desired angle of rotation is set as cos .THETA. and sin .THETA. as a special picture effect by the CPU. A table for the upper picture movement function 83 and a table for the lower picture movement function 84, as the above-mentioned lookup tables, output the movement function f.sub.U (T) for the upper picture and the movement function f.sub.D (T) for the lower picture, with the value of T as the address, respectively.
The movement function f.sub.U (T) for the upper picture, outputted by the table for the upper picture movement function 83, is supplied to multipliers 86, 87. The movement function f.sub.D (T) for the lower picture, outputted by the table for the lower picture movement function 84, is supplied to multipliers 90, 91.
The multiplier 86 multiplies the movement function f.sub.U (T) for the upper picture by cos .THETA. to output a product f.sub.U (T)*cos .THETA. which is outputted to an additive node 85. The additive node 85 adds the linear address X.sub.L to the product f.sub.U (T)*cos .THETA. to give a sum output X.sub.L +f.sub.U (T)*cos .THETA. which is outputted as an X-axis read-out address X.sub.UL for the upper picture, as shown by the equation (6).
The multiplier 87 multiplies the movement function f.sub.U (T) for the upper picture with sin .THETA. to give a product f.sub.U (T)*sin .THETA. to an additive node 88. The additive node 88 adds the linear address Y.sub.L to the product f.sub.U (T)*sin .THETA. to give a sum output Y.sub.L +f.sub.U (T)*sin .THETA. which is outputted as an Y-axis read-out address Y.sub.UL for the upper picture, as shown by the equation (7).
The multiplier 90 multiplies the movement function f.sub.D (T) for the lower picture by cos .THETA. to output a product f.sub.D (T)*cos .THETA. which is outputted to an additive node 89. The additive node 89 adds the linear address X.sub.L to the multiplication output f.sub.D (T)*cos .THETA. to give a sum output X.sub.L +f.sub.D (T)*cos .THETA. which is outputted as an X-axis read-out address X.sub.DL for the lower picture, as shown by the equation (4).
The multiplier 91 multiplies the movement function f.sub.D (T) for the lower picture with sin .THETA. to give a product f.sub.D (T)*sin .THETA. to an additive node 92. The additive node 92 adds the linear address Y.sub.L to the product f.sub.D (T)*sin .THETA. to give a sum output Y.sub.L +f.sub.D (T)*sin .THETA. which is outputted as a Y-axis read-out address Y.sub.DL for the lower picture, as shown by the equation (5).
An output T of the additive node 81 is supplied to an FC table as later explained so as to be used as an address for having reference to an effective area detection flag Fc as later explained.
The above-described circuit shown in FIG. 5 is a circuit portion for generating various addresses for generating the page-turning effect, and is termed a page-turning address generating circuit.
The above-described conventional special effect picture device, inclusive of the page turning address generating circuit shown in FIG. 5, is explained by referring to FIG. 6.
The conventional special picture device is arranged as shown in FIG. 6.
Video input data are stored in a video memory 101 as a frame buffer memory. Key signals are stored in a key memory 102. There are two types of the key signals, one of which is a picture frame signal corresponding to a picture frame supplied from a picture frame key signal generating unit 103. The other key signal is an external key signal employed when accepting an optional shape and may be a letter or character signal for Telop or a key signal generated by a chroma key unit. These two types of the key signals are changeover-selected by a changeover switch 104. That is, the external key signal and the picture frame signal from the picture frame key signal generating circuit 103 are fed to an input fixed terminal a and an input fixed terminal b of the changeover switch 104. One of the two types of the key signals is supplied by setting of a movable output terminal c of the changeover switch 104 to the key memory 102.
A linear address generating circuit 105 adds the effects of contraction, enlargement, movement or rotation to basic addresses H and V, as two-dimensional addresses indicating the positions of the respective sampling points of video and key outputs, in order to generate the linear addresses X.sub.L, Y.sub.L, which are routed to a page turning address generating circuit 106, which is the non-linear address generating unit.
As explained with reference to FIG. 5, the page turning address generating circuit 106 transmits the X-axis read-out address X.sub.DL and the Y-axis read-out address Y.sub.DL for the lower picture of the page turning effect shown in equations (4) and (5) to an effective area detector 107a and to a fixed input terminal a of a changeover switch 108, while transmitting the X-axis read-out address X.sub.UL and the Y-axis read-out address Y.sub.UL for the upper picture of the page turning effect shown in equations (6) and (7) to an effective area detector 107b and to a fixed input terminal b of a changeover switch 108. The read-out addresses X.sub.DL and Y.sub.DL are referred to herein as the read-out addresses for the lower picture (X.sub.DL, Y.sub.DL), while the read-out addresses X.sub.UL and Y.sub.UL are referred to herein as the read-out addresses for the upper picture (X.sub.UL, Y.sub.UL).
The effective area detectors 107a, 107b evaluate the values of the read-out addresses (X.sub.DL, Y.sub.DL) for the lower picture and the values of the read-out addresses (X.sub.UL, Y.sub.UL) for the upper picture and, if the addresses are effective addresses corresponding to an actually existing picture, output a high-level signal "H" as effective area detection flags Fa and Fb, respectively. Since the read-out addresses are defined for the totality of output sampling points, there are generated read-out addresses outside of the range of the effective addresses of the video memory 101 as the frame buffer memory as far as the arithmetic-logical operations are concerned. The picture data read out with the read-out addresses exceeding the effective addresses of the video memory 101 are indefinite picture data. In addition, if the upper picture is superimposed on the lower picture as in the case of page-turning, it is necessary to define an area in which the upper picture is outputted so that the upper picture, if found to be ineffective, can be switched to data for the lower picture. For this reason, the two effective area detection units 107a and 107b are provided in association with the read-out addresses for the lower picture (X.sub.DL, Y.sub.DL) and the read-out addresses for the upper picture (X.sub.UL, Y.sub.UL), respectively, so that the effective area detection flags Fa, Fb will be outputted if the read-out addresses are effective addresses.
Meanwhile, the page turning address generating circuit 106 is responsive to the linear addresses X.sub.L, Y.sub.L supplied from the linear address generating circuit 105 to output the effective area flag Fc indicating an effective area in the L-axis direction of the (X:Y:Z) coordinate system. With the page turning, there disappears a picture beyond a certain point on the axis T because of the picture folding effect. Thus, the table 84 for f.sub.D (T) outputting the lower picture movement function f.sub.D (T) or the table 83 for f.sub.U (T) outputting the upper picture movement function f.sub.L (T) cannot define table data which are f.sub.D (T) or f.sub.U (T), respectively. Thus the read-out addresses calculated by the equations (4) to (7) contain ineffective addresses. It is the effective area detection flag Fc that indicates an area free from the ineffective addresses.
The effective area detection flag Fc may be read out from an Fc table 93 shown in FIG. 5. That is, the effective area detection flag Fc is pro-written in a 1-bit lookup table, under control by the CPU, such that the value T of the T-axis may be found by having reference to the Fc table 93 which is the above-mentioned lookup table.
Returning to FIG. 6, the changeover switch 108 is used for changing over the read-out address between the read-out addresses for the upper picture (X.sub.UL, Y.sub.UL) and the read-out addresses for the lower picture (X.sub.DL, Y.sub.DL), and has its changeover operation controlled by an AND gate 109 as will be explained subsequently.
A changeover switch 112 is used for replacing an area of data read out from the video memory 101 by a black level if the data is invalid, and is controlled as to its changeover operation by an AND gate 111 as will be explained subsequently.
A changeover switch 113 is used for replacing an area of data read out from the key memory 102 by data "0" if the data is invalid and, similarly to the changeover switch 112, has its changeover controlled by the AND gate 111.
The effective area flag Fa of the effective area detection unit 107a is supplied to an OR gate 110, while the effective flag Fb of the effective area detection unit 107b is supplied to the OR gate 110 and an AND gate 109 and the effective area flag Fc of the page turning address generator 106 is supplied to the AND gates 111 and 109. An output of the OR gate 110 is supplied to the AND gate 111.
Thus, if both the effective area detection flag Fb and the effective area detection flag Fc are both "H", that is if the read-out address for the upper picture (X.sub.UL, Y.sub.UL) are effective addresses and the linear addresses (X.sub.L, Y.sub.L) are effective addresses, the AND gate 109 causes the movable contact c and the fixed terminal b of the changeover switch 108 to be connected to each other to select the read-out addresses (X.sub.UL, Y.sub.UL) for the upper picture.
The AND gate 111 is fed with an effective area detection flag Fc and an output of the OR gate 110 fed with the effective area detection flags Fa and Fb. Thus, when the effective area detection flags Fa, Fb and Fc are all "H", that is when the upper picture read-out addresses (X.sub.UL, Y.sub.UL), lower picture read-out addresses (X.sub.DL, Y.sub.DL) and the linear addresses X.sub.L, Y.sub.L are effective addresses, the AND gate 111 allows the movable contact c of the changeover switch 112 to be connected to its fixed terminal b for selecting the output data of the video memory 101. If otherwise, the AND gate 111 causes selection of the black level supplied from the movable contact c.
Similarly, when the effective area detection flags Fa, Fb and Fc are all "H", that is when the upper picture read-out addresses (X.sub.UL, Y.sub.UL), lower picture read-out addresses (X.sub.DL, Y.sub.DL) and the linear addresses X.sub.L, Y.sub.L are effective addresses, the AND gate 111 allows the movable contact c of the changeover switch 111 to be connected to its fixed terminal b for selecting output data of the key memory 102. If otherwise, the AND gate 111 causes selection of data "0" supplied from the movable contact c.
With the above-described conventional special effect picture device, since the upper picture read-out address is changed over to the lower picture read-out address and vice versa, edge serrations caused by switching between the upper and lower pictures at the sampling points are produced in an area 124b shown in FIG. 7. On the other hand, since the key signal is changed over to "0" by the changeover switch 113 in an area 124a of FIG. 7, the key signal K becomes devoid of a gradient, so that edge serrations are similarly produced on synthesis by the switcher.
That is, the pictures are changed over suddenly at a certain point if the key signal is devoid of the gradient. If the input video signal V.sub.1, background signal V.sub.2 and the key signal K are digitized by A/D conversion, the pictures are changed over suddenly at a certain sampling point, so that edge serrations are produced with the sampling point as the edge.
The position and the shape of the edge serrations produced in the above-described page turning effect are as shown in FIG. 7, in which, if the page-turning effect of folding a left-hand edge 123 of a paper sheet 122 is to be manifested on a screen 121 of a monitoring device, there are produced edge serrations on the boundary areas 124a, 124b between the background signal V.sub.2 and the video signal V.sub.1, as shown to an enlarged scale at 124. These edge serrations deteriorate the accuracy of the special effect picture.